mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-18 18:23:53 +08:00
ae120d9edf
When a CPU is running a process, the ASID for that process is
held in a per-CPU variable (the "active ASIDs" array). When
the ASID allocator handles a rollover, it copies the active
ASIDs into a "reserved ASIDs" array to ensure that a process
currently running on another CPU will continue to run unaffected.
The active array is zero-ed to indicate that a rollover occurred.
Because of this mechanism, a reserved ASID is only remembered for
a single rollover. A subsequent rollover will completely refill
the reserved ASIDs array.
In a severely oversubscribed environment where a CPU can be
prevented from running for extended periods of time (think virtual
machines), the above has a horrible side effect:
[P{a} denotes process P running with ASID a]
CPU-0 CPU-1
A{x} [active = <x 0>]
[suspended] runs B{y} [active = <x y>]
[rollover:
active = <0 0>
reserved = <x y>]
runs B{y} [active = <0 y>
reserved = <x y>]
[rollover:
active = <0 0>
reserved = <0 y>]
runs C{x} [active = <0 x>]
[resumes]
runs A{x}
At that stage, both A and C have the same ASID, with deadly
consequences.
The fix is to preserve reserved ASIDs across rollovers if
the CPU doesn't have an active ASID when the rollover occurs.
Cc: <stable@vger.kernel.org> # 3.9
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Catalin Carinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
|
||
|---|---|---|
| .. | ||
| alpha | ||
| arc | ||
| arm | ||
| arm64 | ||
| avr32 | ||
| blackfin | ||
| c6x | ||
| cris | ||
| frv | ||
| h8300 | ||
| hexagon | ||
| ia64 | ||
| m32r | ||
| m68k | ||
| metag | ||
| microblaze | ||
| mips | ||
| mn10300 | ||
| openrisc | ||
| parisc | ||
| powerpc | ||
| s390 | ||
| score | ||
| sh | ||
| sparc | ||
| tile | ||
| um | ||
| unicore32 | ||
| x86 | ||
| xtensa | ||
| .gitignore | ||
| Kconfig | ||